As snow.
Does your wife know of any recent attention regarding procedures for handling bullying?
Somebody mentioned the possibility that somebody else wrote the note. It would be a pretty stupid 5th-grader who forged a note like that when the story could easily be disproven. I wonder if somebody else forged the note and this 5th-grader’s parents went to the school blazing mad, thinking the threat was real, and the school felt like they had to respond this way to avoid a lawsuit from the other direction.
In any case, the origin of the note needs to be investigated, and that should have been done much more discreetly than it was.